Hypertension is a leading cause of morbidity and mortality and is a key contributor to myocardial infarction, stroke, and heart failure. Oxidative injury and inflammation have been implicated in the genesis of hypertension, but the relationship between these is poorly understood. We have recently shown that isoketal-modified proteins accumulate in dendritic cells (DCs) and promote T cell activation and hypertension. Activated T cells infiltrate the kidney and vasculature and promote renal sodium reabsorption and vascular remodeling and fibrosis. Isoketals, or ?-ketoaldehydes, are lipid oxidation products that rapidly react with lysines, and we have found that these modified proteins seem to act as neoantigens in hypertension. We have also observed these in monocytes of hypertensive humans, and suspect they contribute to human hypertension. Our preliminary data indicate that isoketals are formed by reactive oxygen species (ROS) generated by the NADPH oxidases. In aim 1, I will test the hypothesis that the DC NADPH oxidase is critical for the formation of isoketals, and ultimately for T cell activation and hypertension. To accomplish this, I have developed mice in which p22phox, a critical subunit of all rodent NADPH oxidases, is deleted in myeloid DCs and activated macrophages, by crossing mice in which the coding region of p22phox is flanked by loxP sites (p22phoxloxp/loxp mice) with mice expressing Cre recombinase driven by the CD11c promoter. I will examine the effect of p22phox deletion on the ability of DCs to activate T cells, process and present antigens in both MHC-I and MHC-II. I will also examine the hypertensive response to angiotensin II and DOCA-salt challenge in these animals. In aim 2, I will test the hypothesis that the endothelial cell NADPH oxidase contributes to DC activation and formation of DC isoketal-adducts. This hypothesis is based on the concept that stimulated monocytes become activated DCs upon interaction with the endothelium, and I propose that the endothelium is primed to do this in hypertension. For this aim, I have crossed the p22phoxloxp/loxp mice with mice expressing Cre recombinase driven by an inducible (VE)-cadherin promoter. These animals will allow me to specifically delete p22phox in endothelial cells, and I will then examine how loss of the endothelial cell NADPH oxidase affects the hypertensive response to angiotensin II. I will determine how the endothelial NADPH oxidase modifies DC by conducting adoptive transfer of monocytes from GFP transgenic mice to my transgenic mice. In both aims, I will use flow cytometry to monitor DC maturation and isoketal-adduct content and determine how T cells are activated by examining their proliferation in response to DCs. Completion of these studies will lead to the identification of the main source of ROS that is responsible for the formation of isoketals in DCs that, in turn, promote inflammation and hypertension.